I put the Bosch Platinum +4 in my 300E about a month ago and they do not seem to provide any significant change from the regular Platinum plugs. Although the plugs were changed as a matter of maintenance and because of a problem that I was trying to track down or fix. Fortunately, due to a friend in the autoparts business, they were no more expensive than the regular Platinum plugs.
'86 Alfa Romeo Spider
'84 Harley Davidson FLH"X"
'70 FJ40 Land Cruiser (basket case)